This invention pertains to installations for circulating water in potable water piping systems and more particularly in the fire hydrants and dead ends of a municipal water distribution network.
It is well known that microorganisms and suspended solids in potable water vary widely in composition depending on the source, and form microbial growth and sedimentation on the surfaces of piping and reservoirs wherever the water is contained. It is also well known that the sedimentation and the accumulation of microbial growth in still water promote the proliferation of various bacteria and cause the contamination of the water.
Plumbing regulations and plumbing codes are very explicit about preventing cross connections in a piping system and generally, licensed plumbers are apprehensive of these problems. A xe2x80x98cross connectionxe2x80x99 is defined in plumbing code books as any actual or potential connection between a potable water system and any source of pollution or contamination.
It is generally well accepted that stagnant water should always be considered contaminated and non-potable. Further, it is believed that stagnant water is not only found in marshes and ponds, but is also found in water distribution piping systems and reservoirs that do not have sufficient flow to keep the water active, where water remains still for long period of time for example. Although the fact is often neglected, decaying water in a piping system is in direct contact with potable water and represents a cross-connection contamination that is believed to be harmful to the health of users supplied in water by that piping system.
Generally, municipal water distribution systems are flushed periodically to discharge stagnant water. It is often the case that the discharged water has a foul odor and filthy discoloration. Despite these periodic flushes, it is believed that the stagnation of water in municipal piping systems is a major cause of bad water taste, buildup of sediments in residential hot water reservoirs, and microbial growth in toilet reservoirs and in the drains of bathroom accessories. It is further believed that stagnant water in a piping system is a source of many persistent illnesses, digestive problems and the beginning of many diseases to those using and drinking water from these systems.
Another reason for periodically flushing water distribution systems is to eliminate concentrations of chlorine or other disinfectant used in water supply systems which tend to accumulate at regions of low flow or of stagnation. In addition to being detrimental to a good health, high concentrations of chlorine in particular, are known to change the PH value of the water and to deteriorate the protective coating inside water pipes. The material of fabrication of the pipes, which may contain traces of toxin substances are then exposed to the potable water.
The problem of water stagnation is particularly noticeable near water hydrants for example and at the ends of long branches of a piping system where the number of users on a branch pipe is not sufficient for ensuring a proper circulation of water. These situations are often found in newer or partly built subdivisions, and at the end of streets which are supplied in water by oversized pipes. Furthermore, a number of municipalities have water supply systems that were designed according to fire fighting requirements. The size of many branch pipes in these systems is often too large to ensure an adequate circulation of water within the pipe under normal conditions.
The problem of stagnant water in potable water distribution systems has been partly addressed in the past, as can be appreciated from the following prior art documents:
U.S. Pat. No. 2,445,414 issued on Jul. 20, 1948 to W. F. Zabriskie et al. This document discloses a partitioned riser pipe leading to a hydrant, in which water is circulated upward in one side of the pipe and down in the other side. The partitioned pipe is used to circulate water in the casing of the hydrant to prevent freezing of the water inside the hydrant head.
U.S. Pat. No. 3,481,365 issued on Dec. 2, 1969 to A. R. Keen. This patent discloses various partitions in a piping system to divert the water flow near the branch valves in that piping system. The partitions are used to prevent stagnation of water near the branch valves.
U.S. Pat. No. 5,476,118 issued on Dec. 19, 1995 to Ikuo Yokoyama. This document discloses the use of a venturi eductor and venturi tube in an active water pipe to draw water from a valve body in a branch pipe connected to this water pipe, to prevent stagnation of water in the valve body.
U.S. Pat. No. 6,062,259 issued on May 16, 2000 to Blair J. Poirier; the applicant of the present patent application. This document describes a system for recirculating water in the branches of a municipal water distribution system. The main feature of this invention consists of a pumping system having means to draw water from the far end of a branch pipe relative to the water main and to convey this water into the near end of the branch pipe to circulate the water in the branch pipe.
CA 2,193,494 issued on Dec. 07, 1999 to Perry et al. This document discloses a method of cleaning and maintaining potable water distribution pipe system with a heated cleaning solution. The heated cleaning solution is circulated in the piping system to dislodge and flush all accumulated contaminants.
Although substantial efforts have been made in the past to propose solutions to prevent the stagnation of water in piping systems, these proposals continue to be treated with uncertainty by water system designers. For this reason basically, it is believed that there continues to be a need for a better solution which is more practicable than the prior art proposals.
In the present invention, however, there is provided three potable water circulation systems which are related to each other due to several common features. The potable water circulation systems according to the present invention are relatively easy to build, easy to install and to operate. The water circulation systems according to the present invention are believed to be compatible with the current waterworks design practices and fire prevention requirements of a municipal water distribution system.
Broadly, in accordance with one aspect of the present invention, there is provided a potable water circulation system for circulating water in a municipal water distribution network which has a water main and at least one branch pipe extending from the water main. As it is often the case, the branch pipe has a dead end therein at a distance from the water main. The potable water circulation system comprises a conduit system inside the branch pipe, connected to the dead end and to the water main for circulating water from the water main to the dead end and back into the water main. The potable water circulation system also comprises a pump and check valve arrangement connected to the conduit system to cause a minimal circulation of water in the conduit system when a water demand in the branch pipe is lower than the nominal capacity of the pump, and to cause the circulation to reverse when the demand in the branch pipe exceeds the nominal capacity.
The major advantage of this circulation system is that the minimal circulation through the dead end of the branch pipe during low demand periods eliminate the risk of water stagnation in this dead end, while allowing full pipe flow in the branch pipe in the case of an emergency when a fire hydrant is opened for example.
In accordance with another aspect of the present invention, the conduit system is formed by a partition inside the branch pipe and a return gap in this partition at the dead end. One of the advantages associated with such partitioned pipe of that its installation does not require more excavation work than the installation of a conventional municipal water distribution pipe.
In accordance with another aspect of the present invention, there is provided a potable water circulation system for circulating water in a municipal water distribution network comprising a water main and a branch pipe extending from the water main and having a dead end therein at a distance from the water main. The potable water circulation system comprises a first longitudinal partition mounted inside the branch pipe and defining a first and second pipe halves, and a first gap in the first longitudinal partition at the dead end. The potable water circulation system also has a first and second takeoff pipes connected respectively to the first and second pipe halves and separately to the water main. A check valve is mounted in the first takeoff pipe. The check valve has an unchecked side near the water main and a checked side away from the water main. There is also provided a pump having an intake pipe and a discharge pipe connected to the first takeoff pipe, astride the check valve, on the unchecked and checked sides respectively. The pump is operable to cause a circulation of water from the water main, into the first pipe half, through the first gap and back to the water main along the second pipe half, to prevent water stagnation in the dead end.
In yet another aspect of the present invention, there is provided a fire hydrant lateral connected to the branch pipe. This fire hydrant lateral has a second longitudinal partition therein defining a third and fourth pipe halves there along. The fire hydrant lateral also has a hydrant base defining an end thereof and a second gap in the second longitudinal partition in the hydrant base. In this aspect of the present invention, the third and fourth pipe halves communicate with the first pipe half and form with the first pipe half and the second gap a serial conduit.
In yet a further aspect of the present invention, the fire hydrant lateral connected to the branch pipe comprises a directional/bypass valve to selectively direct a flow of water along the third and fourth pipe halves there through, and divert a flow of water from the third pipe half to the fourth pipe half.
In yet another aspect of the present invention, the directional/bypass valve comprises a butterfly valve having an upstream side and a downstream side, and partitioned adapters mounted on the upstream and downstream sides. These adapters have a simple structure manufacturable by conventional metalworking processes or by moulding or casting for examples. This directional/bypass valve is thereby manufacturable with commercially available components and tooling.
The potable water circulation systems according to present invention reduces the difficulties and disadvantages of the prior art water circulation proposals, as the circulation systems described herein are compatible with conventional design and installation practices applicable in this field of waterworks. The potable water circulation systems according to the present invention are manufacturable using current technologies, and do not adversely affect the emergency capacity of a municipal water distribution network.
Other advantages and novel features of the present invention will become apparent from the following detailed description.